Exit Activities and Discontinued Operations - Schedule of Retention Benefit Liability Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended		27 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021
Restructuring Reserve [Roll Forward]
Other current liabilities	$ 156	$ 133	$ 156
Retention Benefits | D.E. Karn Generating Complex
Restructuring Reserve [Roll Forward]
Retention benefit liability at beginning of period	11	4
Costs incurred and charged to maintenance and other operating expenses	0	13	16
Costs deferred as a regulatory asset	7	0
Costs incurred and capitalized	1	2
Costs paid or settled	(5)	(8)
Retention benefit liability at the end of the period	14	11	14
Other current liabilities	$ 5	$ 3	$ 5